The present invention relates generally to the field of intraluminal support devices, or stents. More particularly, the present invention relates to balloon expandable and self-expanding stents having a ring structure architecture. Also, the invention relates to delivery and placement systems for deploying stents in a particular area within a body vessel.
Various types of disease conditions present clinical situations in which a vessel of a patient needs to be artificially supported to maintain an open passageway through which fluids, such as blood, can flow. For example, blood flow through an artery can be impeded due to a build-up of cholesterol on the interior wall of the vessel. Also, vessel walls can be weakened be a variety of conditions, such as aneurysms.
Intraluminal support frames, sometimes referred to as stents, provide an artificial mechanism to support a body vessel. Stents are typically tubular-shaped members that are placed in the lumen of the vessel and, once deployed, exert a radially-outward directed force onto the vessel wall to provide the desired support.
Stents are typically positioned at the point of treatment by navigation through the vessel, and possibly other connected vessels, until the point of treatment is reached. This navigation requires the stent to be able to move axially through the vessel(s) prior to deployment, while still maintaining the ability to exert an outward force on the interior wall once deployed. Accordingly, stents typically have radially unexpanded and expanded configurations. In the unexpanded configuration, the stent has a relatively small diameter that allows it to move axially through the vessel. In the expanded configuration, the stent has a relatively large diameter that allows it to exert an outward force on the interior wall of the lumen, thereby providing the desired support to the vessel.
During navigation through the vessel(s), the stent will likely encounter various turns and bends, which requires the stent to have a degree of longitudinal flexibility. Various stent configurations exist in the art that provide this desired flexibility to some degree. One approach utilizes a plurality of interconnected rings. The members that connect the rings provide the stent with flexibility. Unfortunately, the longitudinal flexibility can result in localized radial movement in the stent when the stent encounters a turn or bend. For example, one portion of a ring member may separate from an underlying balloon, which can interfere with navigation.
The present invention provides a stent that includes a ring architecture and axially displaced connector segments. The stent has longitudinal flexibility that facilitates navigation of vessel turns and bends while maintaining stent portions close to the underlying components of the delivery device, such as a balloon and/or catheter. Preferably, the connector segments lie in a circumferentially extending zig-zag pattern.
In one embodiment, a stent according to the present invention comprises a plurality of ring structures, each of which comprises an endless pattern of unit structures. Each unit structure has two lateral arms and a central region disposed therebetween. The central region preferably comprises a peak disposed between two valleys. Also, each unit structure preferably is inverted with respect to the circumferentially adjacent unit structures of the same ring structure. A plurality of connector segments join each pair of ring structures in the stent. Preferably, each connector segment has an undulating portion. Particularly preferable, the undulating portions of circumferentially adjacent connector segments are axially displaced relative to each other. More preferred, the undulating portions of circumferentially adjacent connector segments are axially displaced when the stent is in a radially unexpanded configuration, and axially aligned when the stent is in a radially expanded configuration.
The invention also provides a delivery system for placing a stent at a point of treatment in a vessel. In one embodiment, the delivery system comprises a catheter having a balloon positioned on a distal end. A connector assembly is positioned at a proximal end of the catheter and is adapted to facilitate expansion of the balloon. A stent according to the present invention is disposed on the distal end of the catheter, surrounding the balloon. Prior to placement, the stent is in an unexpanded configuration in which circumferentially adjacent connector segments joining adjacent ring structures are axially displaced relative to each other.
While the invention is defined by the claims appended hereto, additional understanding of the invention can be gained by reference to the attached drawings and the description of preferred embodiments presented below.